Freeze resistant latex



United States Patent Kentucky No Drawing. May ll, 196%, Ser. No. 28,204is Claims. ((1 26t --27) This invention relates to paint latexes andwater dispersion paint compositions containing such paint latexes. Moreparticularly, it relates to a method of enhancing the freeze stabilityof such latexes and paint compositions and to the freeze stablecompositions resulting therefrom.

In recent years, water dispersion paint compositions in which syntheticlatexes prepared by emulsion polymerization are employed as binders havebecome widely accepted for both inside and outside applications. Theadvantages in application as well as the desirable characteristics ofthe resultant coatings or films are well recognized both wit"- in andwithout the paint manufacturing industry. Unfortunately, however, suchpaint compositions are also plagued by certain disadvantages not theleast of which is their general inability to withstand reducedtemperatures ranging from freezing to considerably below freezing. Undersuch temperature conditions, thickening or coagulation occurs renderingthe compositions useless for coating purposes. An obvious butimpractical solution to the problem is to maintain the temperature ofsuch compositions above the freezing point. Both the latex and paintmanufacturers, therefore, have been confronted with the necessity ofimproving the freeze resistance or freeze stability of paint iatexes andpaint compositions to an extent suthcient for such products to withstandnaturally and frequently occurring low temperatures without detriment.

To this end, certain proposals have been made for improving this freezeresistance or freeze stability which have been employed with varyingdegrees of success. One such proposal involves any of various specialtechniques of polymerization whereby latexes are produced which areinherently more freeze resistant. Such techniques, of course, involveexceptionally close operational control which, as a practical matter,may not be possible to the extent necessary to continuously producelatexes of constant freeze resistant quality. A more practical andsuccessful way of combatting the problem is by incorporating in thelatex or paint a material found to impart freeze resistance thereto. Onesuch class of materials found to be reasonably effective includescetrain monohydroxy and polyhydroxy compounds. Another material foundsuitable for this purpose is a freeze resistant agent derived from theplant Grindelia. Both of these types of freeze resistant agents haveproved generally effective in both paint latexes and water dispersionpaint compositions prepared therefrom. However, in instances where suchstabilized latexes and paint compositions are subjected to extendedperiods of unusually low temperatures or are subjected to repeatedfreezings and thawings, they do not appear to be as consistentlyeffective as might be desired even when employed in relatively highconcentrations.

Accordingly, there has been a continued demand for improved freezeresistant agents. It is a principal object of this invention, therefore,to meet this demand. It is a further object of this invention to providean agent which is more consistently effective than either of the twoclasses of agents above described. A further object is to provide anagent which is economical, readily available, constant in quality andnon-detrimental to Water dispersion paint compositions in which it isincorporated. It is a still fu'ther object of this invention to providea method for enhancing the freeze stability of paint latexes as well asthe Water dispersion paint compositions prepared therefrom. It is anadditional object of this invention to provide a freeze stabilizingagent which is consistently effective at low concentrations and atexcessively low temperatures particularly under conditions of repeatedfreezing and thawing.

In accordance with this invention, these objects have been met in aparticularly effective manner. Surprisingly, it has been found that acombination comprising any of various hydroxyl compounds and aderivative of the plant Grindelia when added to a paint latex or to awater dispersion paint composition prepared therefrom results in anunexpected synergistic freeze stabilizing efiect. More particularly,this improved freeze stabilizing effect is obtained by combining with ahydroxyl compound an extract of the plant Grindelia which is soluble inhydrocarbon solvents as well as in alcohols.

The plant Grindelia from which one of the components of the freezestabilizing agent of this invention is derived belongs to the tribeAsteroideae of the natural family Compositae. The genus Grindeliaincludes some 25 spe cies, six or eight of which are found in SouthAmerica. The remainder occur in the United States mostly west of theMississippi River, generally in semi-arid plateau regions. A particularprevalent plant in the United States is the specie G. squarrosa,commonly referred to as curly cup gumweec Other well known species areG. lzumilis, marsh gumweed, G. camporzzm, field gumweed, G. robusra anda South American variety G. discoidea. The various species are perennialor biennial and produce a sticky resinous substance on the stem andleaves and especially on the flower heads from which characteristic isderived the common name gum plant or gum weed. Certain extracts of theplant have been shown to exhibit some utility in certain areas of thepharmaceutical field, but beyond this there has apparently been nofurther investigation of the plant for any purpose.

The component of the freeze stabilizing agent of the p 'esent inventionthat finds its origin in the plant Grindelia is derived therefrom byconventional extraction means. Thus, the finely pulverized plantincluding leaves, flower heads and stems is simply leached bypercolating therethrough any common hydrocarbon solvent, such as VM&Pnaphtha. The extract is a soft, light amber colored acidic resinoussubstance which is substantially soluble in alcohol. This resinoussubstance may be employed in the form of a water soluble salt incombination with a hydroxyl compound to render both latexes and paintcompositions freeze resistant. However, this resinous substance containsapproximately 10% of an alcohol insoluble material which, if separatedand discarded by subjecting the sub stance to further extraction,renders an even superior freeze resistant agent when combined with ahydroxyl compound. It is a preferred embodiment of this invention,therefore, to or iploy in combination with a hydroxyl compound a watersoluble salt of a hydrocarbon solvent exsultant mixture is agitated atroom temperature until solution is complete. When combined with ahydroxyl compound for use in latexes or paint compositions, the aqueoussalt solution may be used in varied concentrations but will generally beemployed as a 10-25% aqueous solution.

The following example illustrates the extraction of the plant Grindeliaand the saponification of the extract. All parts are by Weight unlessotherwise noted.

EXAMPLE 1 1080 parts of the whole plant G. squarrosa is pulverized witha hammer mill and subjected to extraction by simple percolation at roomtemperature with 2000 parts of commercially available VM&P naphtha.After 30 minutes, the resultant slurry is filtered and the filtratesubjected to distillation to remove the solvent, leaving 120 parts of aresinous substance. 100 parts of the resin is dissolved in 900 parts ofmethyl alcohol and the resultant slurry filtered to separate the thealcohol insoluble fraction. On distillation to remove the alcohol, 92parts of purified resinous substance is obtained. 50 parts of thepurified resinous substance is suspended in 2 30 parts of water,neutralized to a pH of -11 with 10% sodium hydroxide and agitated atroom temperature for 10 minutes. Additional water is then added to givea solution.

The hydroxyl compound which forms the other component of the synergisticfreeze resistant agent of this invention may be any of those generallyrecognized to exhibit by itself a freeze stabilizing effect. Among thesemay be mentioned alcohols such as methanol, ethanol, 11- propanol,isopropanol, n-butanol, sec-butanol, isobutanol and the like; alkylCellosolves such as methyl, ethyl and butyl Cellosolve; and glycols andtheir others such as ethylene glycol, diethylene glycol, triethyleneglycol, propylene glycol, dipropylene glycol, tripropylene glycol,diethylene glycol ethylether, diethylene glycol butylether and the like;Of these, ethylene glycol is preferred for economic,'handling andtoxicity reasons.

The amount of freeze resistant agent employed in accordance with thisinvention may be quite widely varied. It has been found, for instance,that improved freeze resistance is imparted to paint latexes and paintcompositions when using as little as about 0.5% by weight of thesynergistic composition based on the weight of the polymer content ofthe latex. This amount may be considerably increased to as much as about15% but the use of the agent in amounts much beyond 15% is not warrentedas a practical matter since little added advantage is gained. The usualpractice will be to employ about 2.06.0% by weight of the polymercontent of the latex in which range unusually stable paint latexes andpaint compositions are obtained.

In order to produce the synergistic effect to its most optimum degree,it is preferable to employ the agent of this invention with itscomponents in a ratio of at least about 7:3 parts by weight, eithercomponent being in the larger amount. Generally, the components will beemployed in equivalent amounts since there is no practical advantagegained by the use of other ratios. Addition of the components as such oras a prepared aqueous mixture may be made to the latex at various stagesof its preparation or to the paint composition prepared therefrom. Sincethe freeze resistant agent of this invention is equally effective inboth, however, it is preferably incorporated in the latex at some stagein its preparation thereof so that full advantage of its unusualproperties may be taken. Accordingly, the freeze resistant agent may beincorporated during emulsion polymerization or it may be added uponcompletion of polymerization. Alternatively, it may be added at any ofvarious other points throughout the process of preparation such as priorto stripping of unreacted monomers. Preferably, however, the agent isadded to the latex after it has been stripped of unreacted monomers andis ready for storage and/or shipment.

Synthetic latexes to which this invention is applicable are any of thoselatexes suitable for paint compositions which are prepared by theaqueous emulsion polymerization of a polymerizable ethylenic compoundeither with itself or with one or more different polymerizable ethyleniccompounds. Examples of such ethylenic compounds are conjugated diolefinssuch as butadiene-1,3, methyl-2-b'utadi-' cue-1,3,chloro-2-butadiene-1,3, piperylene, 2,3-dirnethyl butadiene-1,3 and thelike; aryl olefins such as styrene, vinyl naphthalene,a-i'nethylstyrene, p-chlorostyrene, vinyl toluene, divinyl benzene andthe like; a-methylene carboxylic acids, their esters, nitriles andamides such as acrylic acid, methyl acrylate, methylmethacrylate,acrylonitrile, methacrylonitrile, acrylamide, methacrylamide and thelike; vinyl aliphatic compounds such as the vinyl halides, vinylacetate, methyl vinyl ether, methyl vinyl ketone and the like; andvinylidene compounds such as the vinylidene halides.

While the present invention is particularly directed to improving thefreeze resistance of paint latexes as above described including paintcompositions prepared therefrom, additional advantages are gained by theuse of the freeze resistant agent described herein. Thus, films orcoatings prepared from paint compositions stabilized according to thisinvention quite unexpectedly exhibit superior film clarity,significantly improved adhesion properties as well as a distinctlybetter resistance to water spotting than is found in films and coatingsnot so stabilized.

These unusual advantages are apparently attributable to the presence ofthe derivative of the plant Grindelia.

The following examples further illustrate the invention. In theseexamples, the test procedure comprises placing a sample of a paint latexor a Water paint com position in a covered metal container and thenplacing the container in a refrigerated compartment for 16 hours at thetest temperature. After 16 hours, the container is removed and thefrozen contents permitted to thaw at room temperature. When the contentsreach room tel perature, they are observed for coagulation and viscosityvariation. The contents are then resubjected to the same procedure untilcoagulation occurs or until four cycles are completed. All parts are byweight unless otherwise noted. The weight of freeze resistant agentbeing based on the polymer content of the latex.

EXAMPLE 2 A purality of samples of a styrene-butadiene latex 7 3 i Thedata of Table I illustrate the eflicacy of the present invention. Thelatexes treated with the instant freeze stabilizing agent (Samples 4, 5and 6) exhibit a superior degree of stability than do those latexesstabilized with either component thereof used alone in an equivalentamount. Moreover, this stability has been found to be consistentlyobtained which is not the case when em ploying either componentseparately, particularly the freeze resistant substance derived from theplant Grin delia.

EXAMPLE 3 The procedure of Example 2 is repeated using the product ofExample 1 as the potassium salt. Similar re sults are obtained.

EXAMPLE 4 The procedure of Example 2 is repeated replacing eth yleneglycol with equivalent quantities of methanol. Similar results areobtained for Samples 3-6. Coagulum 1 appears earlier in Sample 2 at bothtemperatures, how

ever.

EXAMPLE 5 The procedure of Example 2 is repeated using the additives inthe amounts indicated below. Results appear in Table II.

The data of Table II illustrates again the synergistic ef fect obtainedby the use of the freeze resistant agent of this invention (Sample 4).When the procedure is repeated numerous times, the excellent resultsshown above with respect to Sample 4 are consistently obtained whilethose obtained with respect to Samples 2 and 3 vary particularly tolesser degrees of stability.

EXAMPLE 6 The procedure of Example 2 is repeated using samples of Dow512R, a commercially available styrene-butadiene latex of the DowChemical Compan and of Elvacet 81-900, a commercially availablepolyvinyl acetate latex of E. I. du Pont. Test temperature is 29 C.Results appear in Table III.

Table 111 Dow 5123 Elvaeet 81-900 Polymer 100 100 100 100 100 100Product of Ex. 1 2 1 2 1 Ethylene glycol 2 1 2 1 N0. of cycles forcoagulum to appear 3 1 4 2 1 4 EXAMPLE 7 When the procedure of Example 6is repeated replacing the product of Example 1 with saponified extractsof G. camporum and G. roburta as aqueous solutions obtained according tothe procedure of Example 1, similar results are obtained.

EXAMPLE 8 The following ingredients are thoroughly mixed and passedthrough a colloid mill.

Ingredient: Parts Rutile (TiO 100 Lithopone 100 Mica Clay 75 Tetrasodium pyrophosphate 2 Casein solution 1 192 Pine oil 4 Water 112 Tothis thoroughly milled slurry is added. 425 parts of the latex ofExample 5. Samples of the resultant paint composition are treated in thesame manner as the latex in Example 5. Similar results are obtainedillustrating the synergism derived when employing a mixture of the twoadditives.

The above examples illustrate the present invention in various of itsaspects. It should be understood, however, that not only is itapplicable to other paint latexes, but the freeze resistant componentderived from the plant Grindelia may be an extract of any of thespecies, employed in the form of other Water soluble salts. Thehydrocarbon solvent soluble extract as previously indicated, moveover,need not be further extracted with an alcohol, although when thesaponified form of the former is used, the results are not quite asoutstanding.

We claim:

1. A freeze-stable latex comprising a synthetic polymer latex producedby emulsion polymerization and as a freeze-stabilizing agent about05-15% by weight of the polymer content of the latex of a combinationconsisting essentially of a hydroxy compound selected from the groupconsisting of ethylene and propylene glycols and a hydrocarbon solubleextract of the plant Grindelia obtained by extracting said plant with ahydrocarbon, said hydrocarbon soluble extract being in the form of asalt selected from the group consisting of the alkali metal and ammoniumsalts, and said hydroxy compound and said extract being in a ratio byWeight of about 7:3-3z7.

2. A freeze-stable latex comprising a synthetic polymer latex producedby emulsion polymerization and as a freezstabilizing agent about 05-15%by weight of the polymer content of the latex of a combinationconsisting essentially of a hydroxy compound selected from the groupconsisting of ethylene and propylene glycols and a hydrocarbonsoluble-alcohol soluble extract of the plant Grindelia obtained byextracting said plant with a hydrocarbon and then extracting theresulting hydrocarbon soluble extract with alcohol, said hydrocarbonsoluble-alcohol soluble extract being in the form of a salt selectedfrom the group consisting of the alkali metal and ammonium salts, andsaid hydroxy compound and said extract being in a ratio by weight ofabout 7:3-3:7.

3. A latex according to claim 1 in which said extract is obtained fromthe plant Grindelia squarroscr and said hydroxy compound is ethyleneglycol.

4. A latex according to claim 1 in which the polymer is astyrene-butadiene polymer.

5. A freeze-stage water dispersion paint composition comprising asynthetic polymer latex produced by emulsion polymerization, a paintpigment and as a freezestabilizing agent about 05-15% by weight of thepolymer content of a latex of a combination consisting essentially of ahydroxy compound selected from the group consisting of ethylene andpropylene glycols and a hydrocarbon soluble extract of the plantGrindelia obtained by extracting said plant with a hydrocarbon, saidhydrocarbon soluble extract being in the form of a salt selected fromthe group consisting of the alkali metal and ammonium salts, and saidhydroxy compound and said extract being in a ratio by weight of about7:3-3:7.

6. A freeze-stable water dispersion paint composition comprising asynthetic polymer latex produced by emulsion polymerization, a paintpigment and as a freezestabilizing agent about 05-15% by weight of thepolymer content of a latex of a combination consisting essentially of ahydroxy compound selected from the group consisting of ethylene andpropylene glycols and a hydrocarbon soluble-alcohol soluble extract ofthe plant Grindelia obtained by extracting said plant with a hydrocarbonand then extracting the resulting hydrocarbon soluble extract withalcohol, said hydrocarbon soluble-alcohol soluble extract being in theform of a salt selected from the group consisting of the alkali metaland ammonium 8 salts, and said hydroXy compound and said extract being2,444,396 Collins et a1 June 29, 1948 in a ratio by Weight of about713-3 :7. 2,556,575 Cubberley et al. June 12, 1951 7. A compositionaccording to claim 5 in which said 2,822,341 Miller et al Feb. 4, 1958extract is obtained from the plant Grindelio squarrosa 2,853,741Chambflfs 6 1959 and said hydroxy compound is ethylene glycol. 52,956,973 HOldSWOrYh 0C 9 8. A composition according to claim 5 in whichthe OTHER REFERENCES polymer b a Stymnebutadlena Polymer Martin et al.Journal of Agricultural Research, volume 42, No. 2, January 15, 1931,pages 5769.

Singer Fundamentals, of Paint, Varnish & Lacquer Technology, 1957,American Paint Journal Company, pages 234237.

References Cited in the tile of this patent UNITED STATES PATENTS2,384,910 Hanson et a1 Sept. 10, 1945

1. A FREEZE-STABLE LATEX COMPRISING A SYNTHETIC POLYMER LATEX PRODUCEDBY EMULSION POLYMERIZATION AND AS A FREEZE-STABILIZING AGENT ABOUT0.5-15% BY WEIGHT OF THE POLYMER CONTENT OF THE LATEX OF A COMBINATIONCONSISTING ESSENTIALLY OF A HYDROXY COMPOUND SELECTED FROM THE GROUPCONSISTING OF ETHYLENE AND PROPYLENE GLYCOLS AND A HYDROCARBON SOLUBLEEXTRACT OF THE PLANT GRINDELIA OBTAINED BY EXTRACTING SAID PLANT WITH AHYDROCARBON, SAID HYDROCARBON SOLUBLE EXTRACT BEING IN THE FORM OF ASALT SELECTED FROM THE GROUP CONSISTING OF THE ALKALI METAL AND AMMONIUMSALTS, AND SAID HYDROXY COMPOUND AND SAID EXTRACT BEING IN A RATIO BYWEIGHT OF ABOUT 7:3-3:7.